I remember reading Shogun (by James Clavell), and how they talked about how the Catholic Church literally divided the world between Spain and Portugal sanctioning conquering, slaughter and taking lands away form native persons in oder to spread "Christianity."

Anyway, that really helped solidify me against organized religion, as I saw it as more of a quest for power over people than being anything spiritual or altruistic.

Anything written by Christopher Hitchens or Richard Dawkins. Sam Harris is another good influence on me.
RR.